Australia's small island neighbours in the South Pacific face an enormous bill to protect their coastal buildings and infrastructure from the impacts of climate change and extreme weather, one they are unlikely to afford.Research out of the University of New England has for the first time sought to determine the extent of coastal buildings at risk across 12 South Pacific island nations, including Vanuatu and Samoa, putting the cost of replacing those in harm's way at almost $24 billion.The study also found that more than half (57 per cent) of the buildings assessed across the 12 countries were within 500 metres of the coast, making them susceptible to damage under current climate conditions and to the more intense extreme weather, rising sea-levels and storm surges projected with further global warming.

The paper, published in the journal Nature Climate Change on Tuesday, is a part of a larger project the researchers carried out for Australia's Department of Foreign Affairs and Trade to help it prioritise its aid effort in the South Pacific. There are 23 countries and territories in the region, with the 12 chosen for the study having the most complete data.

Small island states are regarded as among the most threatened by climate change as they are often low-lying and generally formed of sand and coral. They are also often among the world's poorer nations.Given the size of the risk, the researchers write these countries and territories will struggle to finance the protection of their coastal buildings. And one of the study's authors, Dr Lalit Kumar, said the study did not captured all climate change costs facing South Pacific nations, as there are also significant flow-on impacts to their agriculture and tourism industries."If they were rich and had billions of dollars they could move most of these [coastal infrastructure] assets inland. But these countries do not have that capability," Dr Kumar said."And a lot of these countries do not have any place inland where they can move their assets."The paper points to Kiribati, Marshall Islands and Tuvalu at being particularly at risk, with over 95% of their built infrastructure being located within 500 metres of coastlines. But while other countries, such as Vanuatu, had smaller proportions of their buildings near coasts, the more valuable assets such as ports, refineries and tourist resorts were largely in the danger zone.Dr Kumar said he believed some South Pacific nations will be wiped off the map in the next 50 to 100 years.

"Some of these countries are already buying land in other countries... because they know with the current trends they won't last long," he said.The impact of global warming on poor nations, and who should carry the burden for it, is a heated topic in international climate change negotiations.Rich nations have pledged to mobilise $100 billion a year from 2020 to help poorer nations tackle climate change. But while interim targets have been met, there is still no agreement how to raise the long-term funds.Poorer nations also want a separate way to be compensated for the "loss and damage" caused to them from greenhouse gas emissions, which have historically been released predominantly by rich nations.Dr Simon Bradshaw, climate change coordinator at Oxfam Australia, said the issue of financing for poor nations will be crucial to the success of a new global climate change agreement countries hope to sign at a meeting in Paris later this year.